Treatment Of Heavy Metal Wastewater By Complexation-ultrafiltration Using Copolymer Of Maleic Acid And Acrylic Acid

Complexation-ultrafiltration process has some significant advantages in treatment of heavy metal wastewater, like simple operation, no phase change, good selectivity, high removal efficiency and easy recycling of metal resource, etc. Choosing a water soluble polymer with high capacity to metal ion as complexing agent and investigating its performance in the complexation-ultrafiltration process is of great importance in treatment of low concentration of heavy metal wastewater.In this work, copolymer of maleic acid and acrylic acid with industrial grade (PMA-100), combining with self-made polyvinyl butyral (PVB) hollow fiber UF membrane, was used to investigate the removal of a single metal ion (Cu2+, Zn2+, Ni2+产and Mn2+) from water and the selective separation of Cu2+and Mn2+from binary mixture by complexation-ultrafiltration process.Potentiometric and conductimetric titrations were used to analyze the acid-base properties of PMA-100, and a preliminary study on the kinetics of complexation reactions of PMA-100with the metal ions was conducted. The results show that carboxylic group content of PMA-100is9.5mmol·g-1, and dissociation constant pKmH=6.74. At pH=6.0, the complexation reaction of PMA-100with Cu2+, Zn2+, Ni2+and Mn2+can be completed within5min, reaching a complexation efficiency of99.8%,98.8%,99.0%and99.6%, respectively. In addition, the difference in binding ability of metal ions to polymer has been studied and the relative affinity is Cu2+>Zn2+>Ni2+> Mn2.Taking Cu2+and Mn2+as research objects, the concentration and decomplexation process for polymer-metal complex was investigated. It shows that the concentration of the two metal ions in the retentate increases from10mg/L to almost100mg/L, and the decline of membrane flux is12.6%and15.2%, respectively. The decomplexation and washing process was further performed to regenerate the copolymer. Under the conditions of pH=6, the mass radio of polymer to metal(P/M) was6, removal efficiency of Cu2+and Mn2+with regenerated PMA-100was97.3%and98.2%, respectively. Selective separation of a binary mixture, in which the concentration of Cu2+and Mn2+was10mg/L, was previously studied in total recirculation model. It is proved efficient under the conditions of pH=5and P/M=6, and removal efficiency for Cu2+and Mn2+is99.0%and29.2%, respectively. According to the conditions, the concentration process of the binary mixture was carried out. When the concentration factor is10, the concentrations of Cu2+and Mn2+in the retentate increase from10mg/L to99.3mg/L and31.8mg/L, respectively. Finally, the selective separation of two metal ions is basically realized by washing the retentate with water solution (pH=5), and the concentration of Cu2+in the retentate is99.0mg/L while that of Mn2+reduced to8.2mg/L.